DESCRIPTION: The long term goal of this research project is to determine the biotin requirement of normal individuals and individuals in specific clinical circumstances. The investigator proposes five specific aims to determine: 1) the usefulness of potential indicators of biotin status. 2) Whether the increased urinary excretion of 3-HIA detected previously in some adults and children treated chronically with anticonvulsant reflects biotin deficiency. 3) Whether increased urinary excretion of 3-HIA detected previously in some pregnant women reflects biotin deficiency. 4) Whether biotin deficiency of similar severity to that observed either early or late in human gestation causes increased rates of fetal malformation in the mouse. 5) The enzyme(s) responsible for biotin beta-oxidation.